×

Electrically erasable and programmable non-volatile memory (EEPROM), wherein write pulses can be interrupted by subsequently received read requests

  • US 5,287,469 A
  • Filed: 12/27/1989
  • Issued: 02/15/1994
  • Est. Priority Date: 12/27/1988
  • Status: Expired due to Fees
First Claim
Patent Images

1. A microcomputer comprising an electrically erasable and programmable nonvolatile memory, a central processing unit for executing a program and issuing a data write request and a data read request to said nonvolatile memory, said data write request including a write address and write data and said read request including a read address, and a control circuit coupled to said nonvolatile memory and said central processing unit, said control circuit including timer means for preforming a time-counting operation to generate an operation end signal, first means responsive to said data write request for performing a data write process in which data stored in a first memory cell of said nonvolatile memory designated by said write address is first erased by applying a high voltage and said write data is then written in said first memory cell by applying said high voltage, second means responsive to said operation end signal for causing said first means to terminate said data write process, third means responsive to said data read request issued while said first means is applying said high voltage to said first memory cell in said data write process, for commanding said first means to stop applying said high voltage to said first memory cell to suspend said data write process, for reading out data from a second memory cell of said nonvolatile memory designated by said read address and thereafter for allowing said first means to reapply said high voltage to resume the suspended data write process and fourth means for commanding said timer means to suspend said time-counting operation in response to said data read request issued while said first means is applying said high voltage to said first memory cell in said data write process and for allowing said timer means to resume said time-counting operation after said third means reads out data from said second memory cell, said timer means thereby delaying the generation of said operation end signal.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×